Oxidative stress imposed on cardiac tissue during hypoxia and reoxygenation affects the redox potential of the cells and targets numerous redox-sensitive molecules, including the ones involved in intracellular communication. Protein kinase C (PKC), one of the key signaling kinases, has been characterized as subject to redox control. As an alternate pathway it represents a new paradigm in signal transduction. Although PKC is attributed a significant role in mediating cell responses under ischemia, and in ischemic preconditioning, the mechanisms of its redox regulation are poorly understood. My recent data demonstrate that the key event triggered by both oxidation and classical activation of PKC is the release of zinc ions that allows the conformational changes needed for the initiation of enzymatic activity. In the area of the newly developing field of redox signaling the proposed research plan aims at understanding of the molecular mechanisms of a reversible redox switch in PKC activation and its role in cardiac cell survival. The experiments will be performed on the model of oxidatively stressed neonatal rat cardiomyocytes in culture,and on the Langendorff perfused adult rat heart subjected to global ischemia. They will: Aim1) Identify the molecular mechanism of PKC activation by redox change. Aim 2) Establish the involvement of signaling molecules, intracellular pH, and antioxidants in redox responses of PKC. Aim 3) Determine the role of PKC isoforms in the mitochondrial pathway of apoptosis in cardiac tissue. Aim 4) Identify the pathways of PKC-mediated protection of the heart during preconditioning. The objective is to prove 1) that the redox modifications in PKC mediate the regulation by the enzyme of a specific check point where the decision to live or to die is made, and 2) that the status of PKC redox sensor determines myocyte sensitivity to oxidative stress-induced cell death. The detailed knowledge of the redox control of PKC function will help to direct future therapeutic modalities for ischemia/reperfusion and related disorders. [unreadable] [unreadable]